The present invention relates to a loop filtering method capable of reducing blocking effects and ringing noise, and more particularly, to a loop filtering method capable of reducing blocking effects and ringing noise of a motion-compensated image.
Most picture coding standards including H.263 of the International Telecommunication Union (ITU) and MPEG-1 and MPEG-2 of the International Standards Organization (ISO), use block-based processing for motion estimation and discrete cosine transform (DCT).
This block-based processing induces the well-known blocking effects and a ringing noise, particularly when an image is highly compressed. The blocking effects casue a viewer who views a decompressed image displayed on a screen to see the boundary between the blocks. The typical blocking effects are grid noise in the monotone area and staircase noise along the image edges. The ringing noise induces sinusoidal traces on the practical edges of an image.